Asian Influenza is a highly contagious disease caused by type A influenza virus. Waterfowl are natural hosts of the disease and are usually asymptomatic. There are two forms of AI: Highly Pathogenic Avian Influenza (HPAI), which causes rapid mortality particularly in domestic poultry, and Low Pathogenic Avian Influenza (LPAI), which is a milder form. AI can be transmitted through the respiratory secretions or faeces of infected birds and also through contact with contaminated materials or items such as clothing, equipement and vehicles (Horimoto and Kawaoka, 2001).

AI viruses have a similar structure and consist of two glycoprotein spikes, hemagglutinin (HA) and neuraminidase (NA) and a limited number of M2 proteins that project from the viral surface (NIAID, 2004). The virus is highly pleomorphic, roughly spherical, and filamentous (NIAID, 2004). Inside the virion are eight single-stranded RNA segments waiting to be copied by a host (NIAID, 2004).

Notes

LPAI can rapidly mutate into HPAI (Perdue et al. 1998) and its ability to cause fatal infections in humans (Horimoto and Kawaoka 2001; Guan et al. 2004) is of serious concern. If a human is simulataneously infected with human and AI viruses it is possible a new virus may emerge which could be transmitted from human to human. This has not occurred and the risks of this taking place are small, but the implications would be extremely serious (pandemic)

Lifecycle Stages

The virus replicates itself once inside a host cell. AI uses the genetic material of the host for energy and for the replication process. After viral components are made inside the host cell, the components are released (Sander, 2004).

Habitat Description

Waterbirds, especially Anatidae are natural reservoirs for AI which needs a host to reproduce (Horimoto and Kawaoka, 2001).

Reproduction

AI needs a host to reproduce. Once inside, the virus uses the hosts DNA to replicate itself (Horimoto and Kawaoka, 2001).

Nutrition

AI, like most viruses, has no metabolism. Therefore, the virus does not require any nutrition (Horimoto and Kawaoka, 2001).

Pathway

The virus is spread from one continent to another by migratory birds that are natural hosts for the disease. The virus has the potential to spread through agriculture industry, such as the poultry industry and live poultry markets. The virus has the potential to be spread through the food trade.

The effects of AI are felt worldwide. The virus has had a significant impact on the economy, trade industry, chicken and animal health, and human health ( APHIS, 2004). For instance, in 1983 and 1984 the the United States government destroyed more than 17 million birds at a cost of 65 million dollars due to an outbreak of AI (APHIS, 2004). In 1997, 6 out of 18 people in Hong Kong infected with H5N1 (a subtype, see Avian Influenza Virus for more details on different types) died (CDC, 2004).

Management Info

Control measures include trade restrictions, and biocontrol security measures on farms and at live markets (APHIS , 2004), quarantine (Butcher, G. et al. 2004), surveillance and vaccines. Swift action following an outbreak of HPAI involves depopulation.

Informations on Avian Influenza Virus has been recorded for the following locations. Click on the name for additional informations.

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Impact information

The effects of AI are felt worldwide. The virus has had a significant impact on the economy, trade industry, chicken and animal health, and human health ( APHIS, 2004). For instance, in 1983 and 1984 the the United States government destroyed more than 17 million birds at a cost of 65 million dollars due to an outbreak of AI (APHIS, 2004). In 1997, 6 out of 18 people in Hong Kong infected with H5N1 (a subtype, see Avian Influenza Virus for more details on different types) died (CDC, 2004).

Bosman, A., Broekman, J., Fouchier, R., Kemink, S., Koch, G., Koopmans, M., Kuiken, T., Munster, V., Osterhaus, A., Rimmelzwaan, G., Rozendaal, F., Schneeberger, P., VanDoornum, P., 2004. Avian influenza A virus (H7N7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome. Proceedings of the National Academy of Sciences of the United States of America (PNAS). 101: 1356-1361.Summary: The article presents information on H7N7 as well as other strains of avian influenza viruses. The characteristics of the viruses and how the viruses are spread from poultry to humans is discussed and remains unclear.